Bug/70315 user is not informed of pir project attributes misconfiguration which leads to a 500 error

[EinLama]

Ticket

https://community.openproject.org/wp/70315

What are you trying to accomplish?

Users can no longer disable project attributes that are set as "assignee" within a PIR. When users hover over the disabled toggle switch, there will be an explanatory hover card.

Also added an explanation to disabled toggles within the PIR configuration screen for consistency.

I noticed that the project custom field mapping was missing some specs. Added these as a drive-by improvement.

Screenshots

What approach did you choose and why?

Merge checklist

• [x] Added/updated tests
• [ ] Added/updated documentation in Lookbook (patterns, previews, etc)
• [x] Tested major browsers (Chrome, Firefox, Edge, ...)